1. Field of the Invention
The invention relates to vehicle suspension assemblies, and in particular to a suspension assembly for controlling the position of an axle relative to a vehicle frame during operation of the vehicle. More particularly, the invention relates to a vehicle suspension assembly for maintaining the relative position of the axle, wherein the assembly has reduced complexity, weight and cost due to replacement of conventional suspension assembly beams with a fabricated torque box structure.
2. Background Art
Axle/suspension systems for vehicles arguably are one of the most important structures of a vehicle, because they ensure a comfortable ride to the passengers in the vehicle and protect any cargo that the vehicle may be carrying from excessive shocks. Axle/suspension systems also provide stability to the vehicle by controlling various forces acting on the axle itself, which in turn could cause an unwanted change in position of the axle relative to the vehicle frame. Specifically, such forces operate to alter the vertical, lateral, and/or longitudinal position of the axle in relation to the vehicle frame, and also can cause axle movement such as roll, yaw, and wind-up.
A typical axle/suspension system usually limits the six possible axle motions by incorporating into the suspension assembly, which supports the axle, a number of components that react to and control the various forces. Although such conventional suspension assemblies generally serve their intended function, the number and/or type of components in a typical prior art assembly also contribute unwanted complexity, weight and cost to the suspension assembly.
The present invention significantly lessens the aforementioned problems by reducing the number and/or complexity of parts needed to control the forces imposed on the axle, and specifically by replacing the pair of beams of a typical prior art suspension assembly with a fabricated xe2x80x9ctorque box.xe2x80x9d Depending on the prior art suspension assembly being compared, the present invention incorporating the torque box concept either reduces the number and complexity of parts to save cost and weight, or reduces complexity alone to achieve the same savings. The resulting simplified suspension assembly of the present invention also exhibits design flexibility whereby its suspension characteristics, such as roll rate, for example, can be readily changed for adapting the assembly concept to different types of vehicle requirements.
Objectives of the present invention include providing a suspension assembly for a vehicle which generally maintains the position of the rigid axle relative to the vehicle frame during vehicle operation, by limiting the vertical, lateral, and longitudinal displacement of the axle, as well as roll, yaw and wind-up axle movements.
Another object of the present invention is to provide such a vehicle suspension assembly which has a reduced number and/or complexity of parts, resulting in less weight and cost, and which is xe2x80x9cnon-reactivexe2x80x9d or generally free of significant axle wind-up or torque.
A still further objective of the present invention is to provide such a suspension assembly which is easily adapted to different suspension characteristic needs of vehicles.
These objectives and advantages are obtained by a suspension assembly for mounting an axle on a longitudinally extending vehicle structure, the suspension assembly including a pair of transversely spaced hangers, each one of the pair of hangers being mounted on and depending from the vehicle structure, a pair of longitudinally extending control arms, each one of the pair of control arms having a first end and a second end, the first end of each one of the control arms being pivotally attached to a respective one of the pair of hangers through a bushing, and the second end of each one of the control arms being pivotally attached to a respective one of a pair of axle seats through a bushing, the pair of axle seats immovably capturing a transversely extending axle, a pair of transversely spaced air springs, each one of the air springs being mounted on a selected one of the axle and a respective one of the axle seats, each one of the pair of air springs extending upwardly and being attached to the vehicle structure, and means immovably mounted on and extending between the vehicle structure and the axle, a portion of the means being movable in certain directions for cooperating with the control arms and the air springs to control forces imposed on the axle during operation of the vehicle structure, so that the suspension assembly minimizes wind-up of the axle.